In the past, monorail has been widely used as a transportation system connecting between two sites spaced by a short to middle distance (for example, 5 to 20 km) such as between residential and industrial districts or between downtown and airport. In the monorail, since a rail is supported by bridge piers constructed on the ground at a required interval, there are advantages that the degree of freedom of design of transportation route is high, and the construction cost can be saved due to a reduced land area for construction, as compared with the case of laying rails for a regular railway.
On the other hand, a large drive unit is usually needed to accelerate a vehicle from a stopped condition to a required speed. When such a large drive unit is mounted in the vehicle, it leads to increases in size and weight of the vehicle. Consequently, huge bridge piers are needed to support the rail and the vehicle. This becomes a cause of lowering the degree of freedom of design with respect to the construction of a monorail system. Furthermore, as larger the land area needed to construct the monorail system, the construction cost also becomes higher. Thus, the conventional transportation system such as monorail still has plenty of room for improvement.